ref: 28f3a3aad8d2d73010f1c81080e92f71903f4556
dir: /sys/src/libndb/ndbreorder.c/
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ndb.h>
/*
* reorder the tuple to put x's line first in the entry and x first in its line
*/
Ndbtuple*
ndbreorder(Ndbtuple *t, Ndbtuple *x)
{
Ndbtuple *nt;
Ndbtuple *last, *prev;
/* if x is first, we're done */
if(x == t)
return t;
/* find end of x's line */
for(last = x; last->line == last->entry; last = last->line)
;
/* rotate to make this line first */
if(last->line != t){
/* detach this line and everything after it from the entry */
for(nt = t; nt->entry != last->line; nt = nt->entry)
;
nt->entry = nil;
/* switch */
for(nt = last; nt->entry != nil; nt = nt->entry)
;
nt->entry = t;
}
/* rotate line to make x first */
if(x != last->line){
/* find entry before x */
for(prev = last; prev->line != x; prev = prev->line);
;
/* detach line */
nt = last->entry;
last->entry = last->line;
/* reattach */
prev->entry = nt;
}
return x;
}